This invention relates to varying of magnetic tripping current in a circuit breaker by varying the spring load on the armatures, and, in particular, by varying such spring load simultaneously by means of rotation of a common crossbar. Accordingly, it is a general object of this invention to provide new and improved devices of such character.
This invention utilizes the mechanical variation of springs to adjust the mechanical tripping current level of a multi-pole circuit breaker, it being noted that virtually all magnetic trip devices include a spring loading system.
This invention recognizes that a force on a spring, especially a torsional spring, can be largely varied while maintaining the compactness of its physical appearance.
Generally, in the past, the magnetic trip level of circuit breakers were not variable or adjustable. Thus, since circuit breakers were produced to "standard" conditions, separate selected circuit breakers were required for selected magnetic levels.
Specifically, it is believed that at least one manufacturer offers for sale circuit breakers having adjustable magnetic trip levels by virtue of adjustable gaps. Some such device uses a comparatively large variable gap of 600 to 800 mils.